1. Field of the Invention
The present invention relates to a printing apparatus as follows. That is, marks are formed by adhering toners of K (black), Y (yellow), M (magenta), and C (cyan) on a transport belt. Then, light is emitted from a light-emitting element to the marks to observe reflection lights thereof and to obtain correction data necessary for a color deviation correction and/or a density correction.
2. Description of the Related Art
There has conventionally been known a printing apparatus provided with the following mark sensor (see Japanese Patent Application Laid-open No. H11-272031). That is, the mark sensor emits light to marks formed on a transport belt to receive reflection lights thereof and detects whether positions of the formed marks are appropriate based on the reflection lights. In this printing apparatus, in some cases, toners etc. of the detection marks formed on the transport belt scatter to cause contamination of the mark sensor. Therefore, a transmissive member (contamination prevention sheet) is provided between the mark sensor and the transport belt to avoid the contamination of the mark sensor. Then, a cleaning device cleans the toners adhered to the transmissive member.
However, the printing apparatus described above does not include a configuration for detecting the contamination of the transmissive member. Thus, a problem arises such that whether or not the transmissive member is contaminated can not be judged.
In view of this, an object of the present teaching is to provide a printing apparatus which is capable of judging as to whether or not the transmissive member is contaminated.